1. Field of the Invention
The present invention relates to a high speed circular saw blade having a plurality of teeth with aggressive hook angle, a plurality of generally radial expansion slots, a shallow gullet, reinforcing extended shoulder, carbide cutting elements, and a thin profile for cutting a thin kerf. A slick coating including friction reducing and non-stick compounds reduce resin buildup and further improve the speed of cut of the thin kerf saw blade. The improved performance of the thin kerf saw blade in comparison with conventional carbide blades is attributable to the synergistic effect of optimizing the design parameters for each of the individual structural features and combining the features according to the present invention to obtain surprisingly good results including: superior cutting speed, reduced tip wear, and reduced energy consumption as compared with conventional saw blades.
2. Description of the Prior Art
There are several types and designs of saw blades for cutting different types of material. Conventional circular saw blades have a plurality of teeth spaced about the outer periphery of the blade, and a plurality of expansion slots of various configurations in the outer edges of the blade in order to dissipate stress and prevent heat warpage of the blades. Expansion slots are not new to the industry and are intended to relieve stress, to aid in cleaning out the kerf, to attain straighter cutting action and to achieve other beneficial results. An expansion slot may be formed in a radial direction being directly aligned with the center of the blade, formed in a non-radial direction spaced around the periphery of the blade, formed having a positive angle, or formed at a negative angle. A positive angle is an angle such that the bottom of the slot trails a line extending from the center of the blade to the outer edge of the slot, relative to the direction of rotation of the saw blade. The bottom of a negative angle slot leads the radial line in the direction of rotation of the saw blade. The angle of the expansion slot is sometimes referred to as the "hook" of the slot, with a radial slot having a 0 degree hook, and positive and negative angle slots having positive and negative hooks, respectively. As the saw blade rotates cutting into the wood, the sawdust enters the space between the saw teeth and the face of the saw blade. As the sawdust comes in contact with the cutting edges at the expansion slots it is propelled by centrifugal force along the face of the teeth out of the area between the saw blade and the wood cut.
There are different types of saw blades having expansion slots of various designs for cutting specific types of material. Large diameter saw blades used for cutting green wood generally have diameters of from 30 to 100 inches in diameter. Because of the large size of the blades, green wood blades are generally operated at slow rotational speeds of about 500 to 1200 revolutions per minute (r.p.m.). to achieve a desirable speed at the cutting edges yet prevent damage to the large diameter blades having high peripheral speed. Fresh cut green wood also tends to swell against the blade due to fresh moist sawdust produced by the cutting action binding in the space between the face of the blade and the wood being cut. This causes excessive friction between the blade and the wood, and contributes to heat buildup. To minimize this problem these large diameter green wood blades are provided with wide expansion slots generally from 1/4 to 1/2 inches wide and having a depth of typically 1/4 of the diameter of the blade. The expansion slots are generally formed at a negative angle often with inserts at the trailing edges of the slots.
A drawback to using inserts in the expansion slots of a saw blade is that they tend to permit the blade to flop back and forth which is undesirable for cutting dry woods requiring a true cut. Also, wide slots cannot be used safely for dry woods because the production of hard dry wood splinters and chips can become wedged into wide expansion slots within the blade and thrown outward creating potential harm to the user. The use of narrow expansion slots in dry wood blades reduces the tendency of chips and splinters becoming wedged within the expansion slots and being thrown from the blade.
Most circular saws employed for cutting dry wood or precut wood are high speed saws. Conventional saw blades having a tip angle of about 20 degrees may have a diameter of up to about 30 inches, but generally have a diameter of about 20 inches or less. The rotational speed of the saw is inversely proportional to the diameter of the blade. For example, it is possible to run a 30 inch high speed saw blade at speeds up to about 1725 r.p.m. while a 20 inch high speed saw blade may be operated safely at 3,450 r.p.m., and a 14 inch saw blade may be operated safely at 5,000 r.p.m. Of these high speed saw blades, two types of saw blades frequently used are the "cut-off" saw blade designed for cutting across the grain of the wood, and "rip" saw blades designed for cutting lumber along the longitudinal direction or with the grain of the lumber.
As with the low speed blades, the high speed blades utilize expansion slots to prevent blade warpage due to heat buildup in the blade. Because sawdust buildup adjacent the face is not a problem with high speed blades used for cutting wood, it is not necessary to provide special designs for expansion slots for high speed blades. Typically, such slots are usually about one inch deep for a 12-30 inch blade and about 3/4 inch for a 6 to 12 inch blade. Conventional high speed blades are formed at the same positive slot hook as the teeth of the blade of between about +10 degrees to about +25 degrees; however, the expansion slots may be formed in a radial direction or at a 0 degree hook.